It linked to a Sky and Telescope article that offered ten things that surprised the Principle Investigator on the New Horizons probe. I liked it and shared it to Facebook. I was going to link to the article here and offer commentary on surprised/not surprised. But then the link surprised me by going to a 404 error. Sky and Telescope at least has a clever 404 message:

“Whoops! – You’ve slewed to a target that’s below the horizon. Please wait while we redirect you to our site’s North Star. Slew Faster”

I reported the now broken URL to Sky and Telescope’s Twitter account, but didn’t want to wait to comment on surprises. So I went the main New Horizons web site at http://pluto.jhuapl.edu/ and found this summary of some of the things that surprised the New Horizons team:

“The data returned so far show a surprisingly wide variety of landforms and terrain ages on Pluto, as well as variations in color, composition and albedo (surface reflectivity). Team members also discovered evidence for a water-ice rich crust, multiple haze layers above the surface in Pluto’s atmosphere, and that Pluto is somewhat larger and a bit more ice rich than expected.

“The Pluto system surprised us in many ways, most notably teaching us that small planets can remain active billions of years after their formation,” said Stern, with the Southwest Research Institute (SwRI) in Boulder, Colorado. “We were also taught important lessons by the degree of geological complexity that both Pluto and its large moon Charon display.”

For me, the biggest surprise is the geological complexity of both Pluto and Charon. When I was growing up in the 1980s, it was doctrine that worlds had to be of a certain size to have any geological activity at all after a short time following their formation. We were told that small bodies had no way of continued heating like the Earth, Venus and larger worlds. So they would grow cold and activity would stop – unless it got smacked by a really large asteroid whose kinetic energy partially melted the surface.

Then came the discoveries of Voyagers 1 and 2 – in particular the irrefutable proof of volcanoes on Io. Here was a moon sized body with a VERY active geological life. I imagine the Voyager team was as stunned as the New Horizons team is now. They put their heads together, shared data with other planetary scientists and came up with a theory since verified by other spacecraft. Io and other largish moons in orbits around gas giants like Jupiter and Saturn have strong tidal forces on them, along with competing pulls from other moons. Since their orbits aren’t perfectly circular, these constant tugs generate a great deal of friction, which results in a heat engine for the interior. So we learned that small bodies can have volcanoes and other activities — IF they orbit a body large enough to induce heat producing tides.

This does not likely seem to be the source of whatever internal heat that is causing Pluto and Charon to resurface themselves. Pluto has a fraction of Earth’s mass and doesn’t appear to have the “oomph” for a lack of a more technical term to be heating the interior of Charon. And it seems to be too small to generate it’s own heat. But both bodies show clear signs of resurfacing withing the last few hundred million years, so SOMETHING is at work, we just don’t know what. I’m really looking forward to any theories the astronomers have. My gut feeling would have been that any resurfacing has to be collision induced, somehow. But if it were that obvious, the New Horizons team would have offered that as an explanation.

My second biggest surprise was that Pluto had enough of an atmosphere to produce haze. The blue sky was knock me over with a feather time, but made sense once the New Horizons team mentioned that Nitrogen is a significant component of what little atmosphere Pluto has. Nitrogen in Earth’s atmosphere scatters red and green light pretty well, leaving us with blue in our skies. But I thought that Pluto’s atmosphere was far thinner than even Mars’ atmosphere, so I wasn’t expecting haze visible from space.

One of the surprises in the currently defunct Sky and Telescope article that didn’t surprise me was that Pluto had a heart. We humans love to see patterns whether or not they’re really there. I feel it was inevitable that someone would find some pattern on Pluto worth remarking on.

Something that didn’t surprise the New Horizons team, but surprised me greatly is that Pluto is red. Apparently this has been known for at least a decade from telescope surveys, but I had missed it. It is a completely different mechanism than the iron rusting that makes Mars red.

If you’d like to look deeper into Pluto’s surprises, here are a few more press releases to guide your way: